Attempts to generate the radical cations of nitroalkanes using the standard procedure of exposing dilute solutions in fluorotrichloranethane at 77 K to ionizing radiation gave 1~ yields of the expected prcducts, having a SOMO confined. to oxygen as judged by their e.s.r.
spectra, together with a species whose e.s.r. spectra closely resembles that of NO2 radicals.
It is suggested that these are rearranged cations, (&OR)'. Similar treatment of nitrobenzene and a range of its ring-substituted derivatives gave initial electron loss frcxn benzene TI orbitals, but on annealing these rearranged into radicals similar to those for the nitroalkanes. Althoughnitroalkane andnitroarane radical anions havebeen extensively stu5edbye.s.r. spsctrosco~, we know of no reports concerning the e.s.r. spectra of the corresponding radical cations. According to theory, and to the results of photoelectron spectroscopy,1'2 the SOI%3 for thenitroalkanesis expectedtobe confined to the two oxygen atoins. There are three possible orbitals [n(n.b.), c and r~*] which should be close in energy, as indicated in I, II and III.
4n.b.) @
The expected situation is thus similar to that found for nitrates, where electron addition to give SNOBSresults in conversion fran a planar to a pyramidal structure, the excess electron being primarily on nitrogen, whilst electron-loss gives NO 3., the electron being in a carjsination